Sent emails end up in the recipient's spam folder

You have sent an email to one or more recipients with your STRATO email address and the email does not arrive normally in the inbox, but ends up in the spam folder.

In this article, we explain the possible causes and how you can deal with them.

Common causes

1. Unknown, not trustworthy sender:
If an email comes from an unknown sender that the recipient server does not recognise as trustworthy, the sender address or the sender server is classified as potentially dangerous. This can lead to the email being considered unwanted and possibly being moved to the spam folder.

2. Filter settings of mail services:
Some mail services allow users to make individual filter settings. These filters can be configured so that certain emails do not end up in the inbox. This can lead to legitimate emails being incorrectly marked as spam or moved to other folders.

3. Invalid file types or attachments that are too large:
If an email contains documents or media, such as images, the type of file or the file size may violate the email server's guidelines. In such cases, the email may be blocked or moved to the spam folder.

4. Violation of the provider's spam policy:
Emails could be automatically categorised as spam if their content violates the provider's spam policy. This could be the case, for example, with frequent newsletter emails or if the content is of a questionable nature (e.g. violent, offensive words). It is advisable to follow the provider's guidelines when sending mass emails to avoid accidental categorisation as spam.

5. Blacklist/blocklist entry due to third-party use:
If the email is sent via certain outgoing mail servers that are on blacklists, this could lead to automatic categorisation as spam. This can be caused by a hacked account, the use of a conspicuous VPN service or the presence of certain suspicious URLs in the email. It is important to check the security of your own email accounts and follow common spam prevention practices to prevent such problems.

What you can do

To solve the problem of emails ending up in the recipient's spam folder, you should consider the following solutions:

1. Achieve trusted sender status:
The recipient's email address can be trained as a trusted sender. This can be achieved by ensuring that your sender server is properly configured and has no suspicious activity.

Tip: Activate DMARC/SPF
-> Beispiel: How can I activate DMARC with STRATO?

Creating a contact can help:
The recipient should add you to their contacts so that you are identified as the desired addressee and your next email is more likely to be delivered.

2. Customisation of the filter settings:
The recipient should check their filter settings with the relevant mail service. Make sure that there are no unnecessary rules that could lead to legitimate emails being incorrectly marked as spam. Adjust the settings if necessary.

3. Checking file types and attachment sizes:
Make sure that the file types and attachments contained in your emails comply with the email server's guidelines. Avoid unauthorised file formats (e.g. .exe = executable files are not permitted) and keep attachment sizes within an acceptable range (generally no larger than 10 - 20 MB).

Tip:
It is better to move file attachments to an online storage facility such as HiDrive and only send the share link in the email.

4. Compliance with the provider's spam policy:
Observe the email provider's spam guidelines, especially when sending mass emails such as newsletters. Avoid content that could be considered suspected spam (example topics: Violence/crime, drugs/weapons/illegal, obscenity, advertising/sales, phishing, hate/incitement, religion, etc.) and adhere to the provider's guidelines to ensure correct delivery.

5. Security check and prevention of unauthorised use:
Regularly check the security of your email accounts to make sure they have not been hacked. Avoid using conspicuous VPN services and be careful when using certain URLs in emails. This will help to avoid blacklist entries.

By implementing these solutions, you can reduce the likelihood of your emails being categorised as spam and ensure that they end up in your recipients' inboxes.

Create SPF rule

Create an SPF record (e.g. "Default STRATO mail server") for the domain you are using in the domain administration under DNS settings. You can find instructions on how to do this in our -> FAQ.

The problem cannot be solved with the above steps

Check webmail

Log in to our Webmail and send your e-mail from this web-based programme. Then check whether the e-mail reaches the recipient. This will at least rule out factors caused by an external e-mail programme.

Test with a different e-mail address

Try sending the e-mail with a different e-mail address.

If the problem persists after carrying out the above steps, the recipient can contact their email provider to clarify whether there are any problems with receiving messages.

Further information:

Why are my emails not being delivered?